On a warm night in July 1986, the writer Andre Dubus pulled over on a stretch of Massachusetts highway to help a young couple, a brother and sister, in a disabled car. Within a few minutes, a distracted driver ran into the three of them at nearly 60 miles an hour.

The young man died instantly. Mr. Dubus (pronounced dub-YOOSE) saved the man’s sister by shoving her out of the way. He himself was hit so hard, his son Andre Dubus III writes in “Townie,” his powerful new memoir, that “in his left front pocket a quarter was bent in half.” He was 50. His legs were crushed. He would never walk again.

When the police arrived, Mr. Dubus, barely conscious, told them about the guns he was wearing on his now-broken body, three of them: a snub-nosed .38, a single-shot Derringer and a .380 semiautomatic. He carried guns for a lot of reasons, his son coolly notes in “Townie.”